Dosage-dispensing units of this type are used to dispense measured doses of substances with high precision. This involves delivering a desired quantity of substance from the dosage-dispensing unit into a target container. Such target containers are in many cases set on a balance in order to weigh the quantity of the substance discharged from the dosage-dispensing unit, so that the substance can subsequently be processed in accordance with given instructions.
A dosage-dispensing unit described in U.S. Pat. No. 5,348,188, which is an invention of the present inventor, includes a housing with a receptacle for dosage material and with a dispensing head consisting of an elastomeric material. The dispensing head is designed like the nipple of a baby bottle and has a slit-shaped outlet which can be opened from the outside by applying a lateral force or pressure from two opposite sides. To prevent the dosage material from conglomerating into powder bridges during the dispensing process, a needle-shaped actuator is arranged to break them up. Before the dispensing operation is started, the needle-shaped actuator is pushed from the side through the elastomeric material and advanced far enough that the point of the needle reaches through the slit-shaped outlet. With this dosage-dispensing unit, it is possible to dispense the smallest quantities of powdery dosage material with high precision. However, the arrangement has the drawback that by reaching through the slit-shaped outlet, the actuator prevents the lips of the slit from closing tightly in the vicinity of the actuator, thus leaving a small leak in this area. As long as the substance particles are larger than the width of this leak, this does not present a problem, but with smaller particles it could happen that minute amounts may escape through the leak. To solve this problem, the needle-shaped actuator can be pulled back far enough, so that its needle point is inside the dispensing head. However, it is also possible for leaks to be caused by larger particles that get trapped between the closing lips.
It is therefore the object of the present invention to modify the aforementioned dosage-dispensing unit in such a way that the outlet orifice can always be securely closed.